In a Long Term Evolution (LTE) system, uplink control information (UCI) is sent by using a physical uplink control channel (PUCCH). One PUCCH occupies a plurality of orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-s-OFDM) symbols in one slot.
In the LTE system, to improve coverage performance of the PUCCH, a demodulation reference signal (DMRS) of the PUCCH is generated based on a Zadoff-Chu (ZC) sequence. For a given length, the LTE system includes a plurality of sequences. Inter-cell interference may be reduced to some extent when terminal devices of different cells use different sequences with a same length at the same time. However, if two terminal devices in neighboring cells send, on a same time-frequency resource, signals generated based on sequences of different lengths, a signal generated based on a relatively long sequence may cause relatively large interference to a signal generated based on a relatively short sequence, and in this case, how to reduce inter-cell interference needs to be further considered. A concept of a sequence group is introduced to the LTE system. Each sequence group includes sequences of different lengths, and there is relatively high cross-correlation between sequences in a same group.
In the LTE system, an index v of the sequence group is calculated according to a predefined rule, where vϵ{0, 1, . . . ,29}. When a length of a DMRS sequence is greater than or equal to 36, q is determined based on the index v of the sequence group and the following formula:
                    q        =                              ⌊                                          q                _                            +                              1                /                2                                      ⌋                    +                      h            ·                                          (                                  -                  1                                )                                            ⌊                                  2                  ⁢                                      q                    _                                                  ⌋                                                                                                  q            _                    =                                    N              ZC                        ·                                          (                                  v                  +                  1                                )                            /              31                                      ,            
where h is equal to 0 or h is equal to 0 and 1, and NZC is a largest prime number smaller than the length of the DMRS sequence.
Further, a ZC sequence {kq} is determined based on the following formula:
                    k        q            ⁡              (        i        )              =          e                        -          j                ⁢                              π            ⁢                                                  ⁢                          qi              ⁡                              (                                  i                  +                  1                                )                                                          N            ZC                                ,where0≤i≤NZC−1
When the length of the DMRS sequence is greater than or equal to 36, a base sequence {rn} of the DMRS sequence is determined based on the following formula:r(n)=xq(n mod NZC), 0≤n<M,where M indicates the length of the DMRS sequence.
A reference signal sequence (such as a DMRS sequence) is defined as a cyclic shift sequence of the base sequence.
As such, inter-cell interference can be reduced to some extent when at least two terminal devices in neighboring cells use sequences in different sequence groups at the same time.
In a New Radio (NR) system, demodulation reference signals (DMRS) of PUCCHs in different formats are also generated based on sequences. On all OFDM/DFT-s-OFDM symbols for transmitting the DMRS, the DMRS is generated based on a computer generated sequence (CGS) or a Zadoff-Chu (ZC) sequence. However, currently there is no solution for reducing inter-cell interference in the NR system.